One note: Korean is soo much easier. The alphabet is uber phonetic, and there's much fewer tenses than English (it's generally obvious in context what you mean).
Thai is strictly phonetic as well, with only 44 consonants and some easy vowel constructs. I and many others mastered the script in a week. Tones are easy after you learned your first tonal language as well.
I am tending to learn Korean and not Chinese because the Chinese logographs are pointlessly making the whole learning process unrewardingly slow.
I like tonal languages but I also like phonetic scripts like Thai or Korean. Why did the PDRC abandon Bopomofo :( It would make it so much more fun to learn Mandarin or other Chinese languages!
Or let's use IPA for every language. Semantics would be lost, and a mandarin text couldn't be understand by a cantonese speaker, but I don't care. (Just kidding)
Well there's always hanja, but I know 99.99% of Korean is written in hangul (beautiful system, by the way.)
The only major downside I see to Korean is that it joins only Japanese and Mongolian in being an SOV language. "As for the store, father regarding, milk buy to went." >_<
